This invention relates to a spacecraft Attitude and Orbit Control System (AOCS or AOC System) in which peripheral systems such a sun sensors, earth sensors, gyros, jet controls, spin wheels and the like are controlled by an attitude and orbit control electronics unit.
Many types of AOC-systems are known; however, each of the known systems was conceived for an individual application, and is composed of known and commercially available electronic, mechanical and optical modules, etc. Thus, a large number of different types of utility interfaces is required for use with such systems. Moveover, such prior art systems require extensive hardware interfaces, which leads to a significant increase of weight and costs, a decrease of the overall reliability and high power losses.
The known Modular Attitude and Orbit Control System (MACOS) attempts to control external interface problems by using buses, but each of the used processor buses has a limited communication bandwidth, and as a result reduces its real-time capacity as the number of intelligent users rises.
The Attitude and Orbit Control System which is currently used at EUTELSAT, has an AOCE (Attitude and Orbit Control Electronics unit) which is controlled by a microprocessor, while the peripherals usually have no microprocessors. Moreover, the interfaces between the utilities are not standardized (there being 45 different types). Such systems require elaborate hardware interfaces for all utilities (for example, sun sensors, earth sensors, gyro systems, jet controls, spin wheels, telecommand/telemetry (TC/TM) systems, to mention only a few), which in turn causes high production costs. Another very important consideration is the fact that the processing power of the previously used processors cannot be expanded. Furthermore, not only do such prior art systems have high power losses and a high overall weight, they also necessitate high expenditures for very different types of testing and checking systems for the AOC's, the check-out systems in the satellite, and the systems for carrying out dynamic tests with real or simulated sensors and actuators, etc.
It is therefore an object of the present invention to provide an AOCS of the initially mentioned type which ensures a significant reduction of weight and power losses, an increase of safety and reliability, a reduction of component multiplicity and enhanced flexibility.
Another object is to provide a corresponding testing system which ensures the highest possible standardization and universality (while including an existing IV network structure), with minimal expenditures.
These and other objects and advantages are achieved according to the present invention, in which a standard interface is created between the AOCE and all peripherals, and between the AOCE and the TC/TM system. This function-related point-to-point communication, ensures that there will be no limitation of the communication bandwidth, as can happen, for example, in the case of the communication by way of a bus. Also, limitation of processing capacity is avoided by using microprocessors with expandable processing powers (expandable microprocessor, or .mu.P/exp), such as transputers. Furthermore, it is also advantageous to decentralize the processing capability and to ensure a data processing on site (that is, in the periphery). In addition, all functions, such as automatic controllers, modulators, etc. are implements in .mu.P/exp's.
Another important advantage of the invention is that all phases of the AOCE and the AOCS can be tested, and with the including of sensors and actuators, by means of standard testing equipment. The testing system is conceived as an integral component on the IV-network.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.